Hydraulic rotary actuator



Feb. 6, 1962 w. E. HEESE ETAL 3,019,771

HYDRAULIC ROTARY ACTUATOR Filed June 9, 1960 2 Sheets-Sheet 1 FIG FIG. 2

' INVENTORS.

WILLIAM E. HEESE 8: ROBERT E WHITE BY MM .1 mi

their ATTORNEYS 2 Sheets-Sheet 2 WILLIAM E. HEESE 8 ROBERT F WHITE I fi'M meir ATTORNEYS W. E. HEESE ETAL HYDRAULIC ROTARY ACTUATOR Feb. 6, 1962Filed June 9, 1960 FIG 5 ate ited States ice 3,019,771 HYDRAULIC ROTARYACTUATOR William E. Heese, Old Saybrook, and Robert F. White,

Stonington, Conn, assignors to General Dynamics Corporation, New York,N.Y., a corporation of Delaware Filed June 9, 1960, Ser, No. 35,077 2Claims. (Cl. 12138) This invention relates to hydraulic actuators and,more particularly, to an actuator having an output shaft selectivelyrotatable to three positively indexed angular positions.

Hydraulic rotary actuators, which have been adopted for use with manymechanical devices, combine ruggedness and reliability with high torqueoutput when supplied with suitable hydraulic fluid pressures. Ordinarilyrotary actuators positively index their output shafts at two angularpositions. Attempts to provide three position rotary actuators have metwith little success, such units being unduly complicated and uneconomicdevices of relatively great bulk.

The present invention provides a simple compact hydraulic actuatorrotating an output shaft to three positively indexed angular positionswith constant torque. To this end, a preferred embodiment of theinvention includes a housing formed with two parallel firstcylindersslidably receiving piston-like racks operatively engaging a piniondriven output shaft. Two larger cylinders in the housing, slidablymounting floating pistons, extend from the first cylinders. Three portscommunicating with the ends of the cylinders and their junctions areadapted to be connected to fluid supply and return ducts for rotatingthe output shaft to a selected one of the three angular positions.

These and further advantages of the invention will be more readilyunderstood when the following description is read in connection with theaccompanying drawings, in which:

FIGURE 1 is an elevation of a three position hydraulic rotary actuatorconstructed in accordance with the principles of the present invention;

FIGURE 2 is a longitudinal section of the actuator of FIGURE 1 takenalong the view line 22 looking in the direction of the arrows; and VFIGURES 3, 4 and 5 illustrate the hydraulic actuator schematically inits three positively indexed angular positions.

Referring to a typical embodiment of the invention in greater detailwith reference to the drawings, the hydraulic rotary actuator shown inFIGURES 1 and 2 includes a housing formed with suitable mounting flanges11 and 12. The housing 10 may be bolted to a valve housing, for example,to control a three position valve.

A pair of parallel first cylinders 13 and 14 provided in the housing 10slidably receive piston-like racks 15 and 16 carrying O-rings 17 and 18in annular grooves 19 and 20, adjacent to their outer ends, for sealablyengaging the cylinder walls. Threaded plugs 21 and 22 provided withsuitable seals 23 and 24 respectively close the ends of the cylinders 13and 14.

The racks 15 and 16 carry teeth 25 and 26 that operatively engageopposite sides of a pinion 27 mounted in a chamber 27a in the housing10. An output shaft 28, either secured to or integral with the pinion27, is suitably journaled in the housing 10 and extends therefrom in onedirection (as shown) or in both directions, if desired.

A pair of second cylinders 29 and 30 in the housing 10, their endsclosed by threaded plugs 31 and 32 carrying appropriate seals 33 and 34,extend from the open ends of the cylinders 13 and 14 along their axes.The cylinders 29 and 30 have a somewhat greater diameter than thecylinders 13 and 14 for reasons that will become a parent hereinafter,

Floating pistons 35 and 36, slidably mounted in the cylinders 29 and 30,carry sealing O-rings .37 and 38 in annular grooves 30 and 40.Cylindrical recesses 41- and 42, having the same diameter as thecylinders 13 and 14, are cut out of the pistons .85 and 36 to receivethe inner ends of the racks15 and 16, thereby minimizing rockin of thesliding members.

Three fluid ports 43, 44 and 45 in the housing 10, adapted to beconnected to fluid' supply and return ducts, are joined *by fluidpassages to the cylinders 13, 14, 29 and 30. In particular, the port 43is placed in fluid communication with the outer ends of the largerdiameter cylinders 29 and 30 by passages 46, 47 and 48 in the housing10; the port 44 is placed in fluid communication with the outer ends ofthe smaller diameter cylinders 13 and 14 by fluid passages 49 and 50;and the port 45 is placed in fluid communication with (l) the other endsof the cylinders '14 and 30 at their junction by fluid passage 51 and(2) with the other ends of the cylinders 13 and 29 at their junction byopenings 52 and 53 in the inner ends of the racks 16 and 15,respectively, and the chamber 27a. If desired, the fluid passages may beformed by tubing external to the housing 10.

The operation of the hydraulic rotary actuator will be readilyunderstood by referring to the schem-aticdiagrams of FIGURES 3, 4 and 5which illustrate schematically the three positions to which the outputshaft 28 is indexed positively by hydraulic fluid pressure. In theparticular embodiment of the invention described, the shaft 28 isrotated with constant torque to positions at 0, or depending on thesupply and return fluid pressures applied to the ports 43, 44 and 45. Itwill be understood that such positions are illustrative only and thatthe output shaft 28 could be rotated to any three angular positions byvarying the length of the racks 15 and 16 to add or subtract a desirednumber of the teeth 25 and 26 engaging and rotating the pinion 27.Furthermore, the shaft 28 may be rotated through an angle greater than360 between adjacent positions, if desired.

Referring to FIGURE 3, which shows the output shaft 28 at 0 position,fluid supply pressure, designated S, is applied to port 44 and a fluidreturn, designated R, is provided at ports 43 and 45. With thisarrangement, the racks 15 and 16 are urged to positions most remote fromthe plugs 21 and 22, carrying with them the floating pistons 35 and 36,and rotating the shaft 28 to 0.

When it becomes desirable to operate the shaft 28 to its 90 position asshown in FIGURE 4, fluid supply pres sure is applied to the ports 43 and44 while a fluid return is provided at the port 45. Such a combinationof fluid pressures urges the rack 15 and the floating piston 35 inopposition directions toward each other, and the same is also true ofthe rack 16 and the piston 36. However, since the larger diameter of thefloating piston cylinders provides areas upon which the supply pressureacts that are greater than the areas subjected to supply pressure inconnection with the racks, the pistons 35 and 36 are displaced to theinner ends of the cylinders 29 and 30, as show in FIGURE 4, and the endsof the racks 15 and 16 are displaced into the recesses 41 and 42.Accordingly, the output shaft 28 will be rotated to its 90 position.

Finally, to rotate the output shaft 28 to its 180 position, as shown inFIGURE 5 (and also in FIGURE 2), fluid supply pressure is applied to theports 43 and 45 and a fluid return provided for the port 44. Thepressure at the port 43 provides a greater total force on the out-- sideof the floating pistons 35 and 36 than is applied to the inside surfacesthereof by the fluid pressure at the port 45 due to the smaller diameterof the cylinders 13 and 15. However, the fluid pressure at the port 45dis places the racks 15 and 16 outwardly with precisely the same forcethat urges the racks inwardly since the fluid pressure acts effectivelyagainst the same diameter cylinder in both instances.

It will be apparent that the inventive hydraulic actuator provides acompact unit supplying constant torque rotation of an output shaft toany three selected angular positions. The above described embodiment ofthe invention is, of course, illustrative only and modifications thereofwill occur to those skilled in the art. Therefore, the invention is notto be limited to the specific apparatus disclosed herein but is to bedefined by the appended claims.

We claim:

1. A three position rotary hydraulic actuator comprising a housing, anoutput shaft journaled in the housing, a

pinion in the housing on the shaft, first, second and third fluid portsin the housing adapted to be subjected to fluid pressure to control theangular position of the shaft, two first parallel cylinders formed inthe housing, two parallel piston-like racks engaging opposite sides ofthe pinion and respectively slidably mounted in the first cylinders,first fluid passage means providing fluid communi- 4 cation between thefirst port and one end of each of the first cylinders, two secondcylinders formed in the housing and extending from the other ends of thefirst cylinders along their axes, the diameter of the second cylindersbeing greater than that of the first cylinders, two pistons respectivelyslidably mounted in the second cylinders, second fluid passage meansproviding'fluid communication between the second port and the end ofeach of the second cylinders remote from the first cylinder, and thirdfluid passage means providing fluid communication between the third portand the junctions of the first and second cylinders.

2. Apparatus as defined in claim 1, wherein a cylinrical recess isformed in each of the pistons having the same diameter as the firstcylinder to receive one end of each of the piston-like racks.

References Cited in the file of this patent UNITED STATES PATENTS1,623,780 Crocker Apr. 5, 1927 1,806,669 Campbell May 26, 1931 2,095,820Lenz Oct. 12, 1937 2,946,320 Vogel July 26, 1960

